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Early Fermi LAT observations of the Vela pulsar. Massimiliano Razzano on behalf of the Fermi LAT Collaboration. INFN-Pisa massimiliano.razzano@pi.infn.it. ID of Vela pulsar. Radio pulsation discovered in 1968 in the Vela SNR, bright pulsar: S 1.4Ghz ~1.5 Jy - PowerPoint PPT Presentation
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M.Razzano - 44th Rencontres de Moriond
Early Fermi LAT observations of the
Vela pulsar
INFN-Pisamassimiliano.razzano@pi.infn.it
Massimiliano Razzano on behalf of the Fermi LAT Collaboration
ID of Vela pulsarID of Vela pulsar Radio pulsation discovered in 1968 in the Vela SNR, bright pulsar: S1.4Ghz~1.5 Jy
Located RA=08:35:20.61,dec=-45:10:34.87 (near the Galactic plane @b~-2.8˚)
D~287+19-17 pc (VLBI parallax in 2003)
P:~89 ms; Pdot ~3x10-13 s/s
Young pulsar c~11 kyr
Energetic Edot~7x1036 erg/s
Bsurf ~3.4x1012 G
7 high confidence gamma-ray pulsarsLow confidence gamma-ray pulsars(D. Thompson, 2003)
A huge gamma-ray telescope !
020000400006000080000
100000120000140000160000180000200000
Events
SAS-2 COS-B EGRET AGILE FermiLAT
LATexpected(~1 yr)
Collected photons from Vela at different g-ray telescopes
Thompson et al. 1975
Kanbach et al. 1980Kanbach et al. 1994Pellizzoni et al. 2008
Abdo et. al 2008
A huge teamwork !
•Large collaborative effort of
scientific/instrumental analysis!
•See Abdo et al. 2009 ApJ in press,
arXiv:0812.2960
Point Spread FunctionPoint Spread Function
• Flight data on Vela used for testing the pre-launch expectations• The PSF is very sharp at high energy
Excellent agreementwith pre-launchexpectations below few GeV
Stefano Germani’s talk about on-orbit performance
verifications & monitoring
First First Fermi Fermi Vela light curveVela light curve
100 MeV < E < 10 GeV
~50000 photons !
Remarkablysharp peaks;features to ~0.3 ms
Turns almostcompletely offbetween thedouble pulses
Light curve evolution with energyLight curve evolution with energy
Large LAT energy window puts Vela pulsar in multiwavelength context !
Vela in RadioVela in Radio
• Coherent radio emission– Parkes 64m telescope– RMS residuals 90s
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Synchrotron optical/uv– HST STIS/MAMA – 4.1-6.5 eV(Romani et al., ApJ 2005)
Vela in UVVela in UV
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Thermal soft X-rays
–XMM PN
Soft X-raysSoft X-rays
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Synchrotron hard X-rays
–RXTE PCA(Harding et al., ApJ 2002)
Hard X-raysHard X-rays
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
Vela in Vela in gg-rays-rays
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Curvature g-rays– FermiFermi LAT LAT – Energy dependent pulses
• First peak softer than second
– Known from EGRET
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Curvature g-rays– FermiFermi LAT LAT – Energy dependent pulses
• First peak softer than second
– Known from EGRET
Vela in Vela in gg-rays-rays
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Curvature g-rays– FermiFermi LAT LAT – Energy dependent pulses
• First peak softer than second– Known from EGRET
– 3rd Peak, which shift in energy
– New result !
Vela in Vela in gg-rays-rays
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Curvature g-rays– FermiFermi LAT LAT – Energy dependent pulses
• First peak softer than second– Known from EGRET
– 3rd Peak, which shift in energy
– New result !
Vela in Vela in gg-rays-rays
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
Vela in Vela in gg-rays-rays• Curvature g-rays
– FermiFermi LAT LAT – Energy dependent pulses
• First peak softer than second– Known from EGRET
– 3rd Peak, which shift in energy
– New result !
log F(Jy Hz)
log E2 dN/dE(erg cm-2 s-1)
• Curvature g-rays– FermiFermi LAT LAT – Energy dependent pulses
• First peak softer than second
– Known from EGRET
– Trailing peak survives (known from EGRET)
Vela in Vela in gg-rays-rays
Phase-averaged spectrumPhase-averaged spectrum
Consistent with b=1 (simple exponential)
b=2 (super-exponential) rejected at 16.5s
No evidence for magnetic pair attenuation:Near-surface emission ruled out
N(E) N0E e (E /Ec )b
1.51 0.050.04
Ec 2.9 0.1 GeV
The Vela pulsar movie
E<300MeV (red)300MeV<E<1GeV(Green)E>1GeV (blue)
Summary of key resultsSummary of key results• Vela pulsar
– Phase-averaged spectrum• Simple exponential cutoff Ec = 2.9 ± 0.1 GeV• Inconsistent with magnetic pair attenuation, thus favoring outer
magnetosphere emission models– Energy-dependent pulse profile
• First peak is softer than second peak (confirming EGRET)• Sharpest features to ~0.3 ms.• Peak in bridge region (phase ~ 0.3) shifts to later phase with increasing g-ray
energy– Upper limit on unpulsed emission (>100 MeV)
• 1.8x10-7 ph/cm2/s 95% C.L. upper limit on unpulsed emission, e.g. PWN (Talk of Marie-Helene Grondin)
• Stringent limits or measurement will be available with more livetime– See Abdo et al. 2009 ApJ in press, arXiv:0812.2960
• Contact authors R. Romani and M. Razzano• Fermi LAT & Vela
– Working as designed, performance as expected• e.g. Vela results demonstrate timing and angular resolution below few GeV
(Talk of Stefano Germani)
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